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1.
The estuarine chemistry of dissolved humic acids was determined by carrying out both field and laboratory studies. These approaches were combined in an investigation of the Amazon estuary while laboratory mixing experiments were performed using filtered (0.45?0.001 μm) river water fractions of the Water of Luce (Scotland).The results demonstrate that a small fraction of river dissolved organic matter is preferentially and rapidly flocculated during estuarine mixing. This fraction is the high molecular weight component of dissolved humic acids (0.45?0.1 μm filtered). Approximately 60–80% of the dissolved humic acid in these rivers flocculates during estuarine mixing. This represents a removal of only 3–6% of river dissolved organic matter and is responsible for the non-conservative behaviour of dissolved humic acid in the Amazon estuary even though total dissolved organic carbon appears conservative.The salinity dependence with which humic acid flocculates in estuaries is similar to that of iron. This implies that both constituents may be removed from river water by a common mechanism of colloid flocculation. 相似文献
2.
Peter Swarzenski Pamela Campbell Don Porcelli Brent McKee 《Continental Shelf Research》2004,24(19):2357
Natural concentrations of 238U and δ234U values were determined in estuarine surface waters and pore waters of the Amazon and Fly (Papua New Guinea) Rivers to investigate U transport phenomena across river-dominated land–sea margins. Discharge from large, tropical rivers is a major source of dissolved and solid materials transported to the oceans, and are important in defining not only oceanic mass budgets, but also terrestrial weathering rates.On the Amazon shelf, salinity-property plots of dissolved organic carbon, pH and total suspended matter revealed two vastly contrasting water masses that were energetically mixed. In this mixing zone, the distribution of uranium was highly non-conservative and exhibited extensive removal from the water column. Uranium removal was most pronounced within a salinity range of 0–16.6, and likely the result of scavenging and flocculation reactions with inorganic (i.e., Fe/Mn oxides) and organic colloids/particles. Removal of uranium may also be closely coupled to exchange and resuspension processes at the sediment/water interface. An inner-shelf pore water profile indicated the following diagenetic processes: extensive (1 m) zones of Fe(III)—and, to a lesser degree, Mn(IV)—reduction in the absence of significant S(II) concentrations appeared to facilitate the formation of various authigenic minerals (e.g., siderite, rhodocrosite and uraninite). The pore water dissolved 238U profile co-varied closely with Mn(II). Isotopic variations as evidenced in δ234U pore waters values from this site revealed information on the origin and history of particulate uranium. Only after a depth of about 1 m did the δ234U value approach unity (secular equilibrium), denoting a residual lattice bound uranium complex that is likely an upper-drainage basin weathering product. This suggests that the enriched δ234U values represent a riverine surface complexation product that is actively involved in Mn–Fe diagenetic cycles and surface complexation reactions.In the Fly River estuary, 238U appears to exhibit a reasonably conservative distribution as a function of salinity. The absence of observed U removal does not necessarily imply non-reactivity, but instead may record an integration of concurrent U removal and release processes. There is not a linear correlation between δ234U vs. 1/238U that would imply simple two component mixing. It is likely that resuspension of bottom sediments, prolonged residence times in the lower reaches of the Fly River, and energetic particle–colloid interactions contribute to the observed estuarine U distribution. The supply of uranium discharged from humid, tropical river systems to the sea appears to be foremost influenced by particle/water interactions that are ultimately governed by the particular physiographic and hydrologic characteristics of an estuary. 相似文献
3.
Nitrogen over enrichment in subtropical Pearl River estuarine coastal waters: Possible causes and consequences 总被引：1，自引：0，他引：1
Hong Kong is surrounded by estuarine, coastal and oceanic waters. In this study, monthly averages over a 10 year time series of salinity, temperature, chlorophyll a (chl a), dissolved oxygen (DO), dissolved inorganic nitrogen (DIN), silicate (SiO4) and orthophosphate (PO4) at three representative stations around Hong Kong were used to examine if excess nitrogen in estuarine influenced waters is due to P limitation. The monthly distribution clearly shows the dominant influence of the seasonal change in river discharge in the Pearl River estuary and adjacent coastal waters. In winter, the river discharge is small and more oceanic waters are dominant and as a result, salinity is high, and chlorophyll and nutrients are low. In summer, when the river discharge is high, salinity decreases and nutrients increase. DIN is very high, reaching 100 μM in the estuary. This indicates over enrichment of nitrogen relative to P and consequently there is an excess of N in coastal waters of Hong Kong. P remains low (∼1 μM) and can potentially limit both phytoplankton biomass and N utilization which was demonstrated in field incubation experiments. P limitation would result in excess N being left in the estuarine influenced waters south of Hong Kong. Phosphate concentration is lower in the Pearl River estuary than in many other eutrophied estuaries. Therefore, this relatively low PO4 concentration should be a significant factor limiting a further increase in the magnitude of algal biomass and in the degree of eutrophication in the Pearl River estuary. The export of the excess N offshore into the northern South China Sea may result in an increase in the size of the region that is P limited in summer. 相似文献
4.
Edward R. Sholkovitz 《Earth and Planetary Science Letters》1978,41(1):77-86
A laboratory experiment was carried out in which the flocculation products, formed from the mixing of filtered (0.4 μm) river water and seawater, were analysed. This study established that Fe, Mn, Al, Cu, Ni, Cd and Co have resolvable and well-defined estuarine chemistries. Copper, Ni, Mn and Co have salinity dependences of removal which are similar to those of dissolved Fe and humic acids. The amount of removal of the above trace metals increases between 0 and 15–18‰, after which little additional removal occurs. The extents of removal from river water are very different: Fe, 95%; Al, 20%; Cu, Ni, 40%; Co, 10%; Cd, 5% and Mn, 25–45%. The basic removal mechanism appears to be the estuarine flocculation of trace metals which exist, in part, in river water as colloids in association with colloidal humic acids and hydrous iron oxides. A qualitative model, based on this mechanism, supports the observations of this flocculation study.The results of this study give the most complete and consistent set of data presently available, from which to postulate the most important processes controlling the estuarine chemistry of trace metals. The generality of their behaviours still needs to be determined by future investigations. 相似文献
5.
The deterioration of sediments is a serious environmental problem. Controlling nutrient release fluxes from sediments is important to alleviating eutrophication and to reducing terrigenous nutrient loads. The purpose of this study was to evaluate the phosphate removal performance of granulated coal ash (GCA) from seawater, which is produced from coal thermal electric power generation. Batch experiments were carried out to investigate the removal kinetics of phosphate from seawater under both oxic and anoxic conditions. Phosphate was removed well from seawater under both oxic and anoxic conditions. The adsorption isotherm for phosphate revealed that GCA could remove phosphate effectively from seawater above a concentration of 1.7 μmol L−1. GCA can reduce the concentration of phosphate in seawater effectively under anoxic conditions where iron type adsorbents cannot be applied. Therefore, GCA could potentially be used to adsorb phosphate in the organically-enriched sediment, which generally occurs under highly reductive conditions. 相似文献
6.
7.
Brittany R. Kruger Brent J. Dalzell Elizabeth C. Minor 《Aquatic Sciences - Research Across Boundaries》2011,73(3):405-417
In this study, samples were taken from three contrasting freshwater sources and amended with salt in order to determine the
influence of salinity and dissolved organic matter (DOM) composition on DOM recovery via ultrafiltration and solid phase extraction
(SPE) with C18 disks. Salt addition caused variable recovery of DOM when using C18 SPE, and ultraviolet–visible spectroscopic characterization of the extracted material showed spectral responses that varied
among sample sources. In contrast, increasing sample salinity from 0 to 30 ppt consistently caused a 15–25% reduction in the
amount of high molecular weight DOM isolated by ultrafiltration for both dissolved organic carbon (DOC) and chromophoric DOM
(CDOM), regardless of DOM composition. We hypothesize that a change in conformation (such as coiling or disaggregation) of
DOM molecules occurs in the presence of salt, allowing them to pass through the ultrafiltration membrane and thereby decreasing
the DOM retained by ultrafiltration. These results are important because they demonstrate that changes in salinity can influence
DOM recovery in estuaries. Interpretation of DOM characteristics along estuarine gradients needs to account for potential
artifacts introduced by sample isolation techniques. 相似文献
8.
This study investigated the role of the solution composition on calcite precipitation induced by cyanobacteria. The precipitation of calcium carbonate was induced by addition of cyanobacterium cells Synechococcus strain PCC 7942 in two artificial solutions with a different composition at similar saturation states in respect to calcite. Ion‐selective electrodes for pH, Ca2+, and COequation/tex2gif-stack-1.gif monitored the experiments, and the morphology of precipitated crystals was analysed by scanning electron microscopy. The calcite precipitation was observed in all experiments after the addition of the cells. The composition of solution (the ratio of dissolved inorganic carbon to dissolved calcium) strongly influenced the calcite precipitation. Based on laboratory experiment results, a possible mechanism for precipitation induced by Synechococcus is proposed linking precipitation with the conditions near to cell walls rather than with the saturation conditions in the bulk solution. 相似文献
9.
Mohammad Belal Hossain 《国际泥沙研究》2019,34(1):48-57
The trophic structure of a community is used to infer ecosystem functioning (e.g. energy transfer and nutrient cycling). Here the trophic structure of the benthic infaunal and epifaunal communities in the Brunei Estuary are characterized, and their distribution along an estuarine pH gradient is analyzed using univariate and multivariate techniques. This analysis revealed that surface deposit feeders (e.g., polychaetes) were numerically dominant within the infaunal communities whereas in the epifaunal communities filter feeders (e.g., bivalves) were highly abundant. Species richness for almost all trophic groups increased toward the lower estuary, except for omnivores in the epifaunal communities, which decreased markedly. Both Analysis of Variance (ANOVA) and Analysis of Similarities (ANOSIM) detected significant differences in the density of respective trophic groups among stations. Within infaunal communities, both Biological and Environmental procedure (BIO-ENV) and Canonical Correspondence Analysis (CCA) showed that trophic shifts were associated with environmental gradients. Surface-deposit feeders and omnivores were the most abundant macrobenthos of the upper estuary characterized by low salinity, low pH, and a higher percentage of mud particles. The proportion of filter feeders and carnivores increased with salinity/pH and sand. A more uniform distribution of trophic structure was found in the lower estuary, with high salinity and pH over sandy habitat. In contrast, within epifaunal trophic groups, the percentage of surface deposit feeders and omnivores declined, but filter feeders remarkably increased toward the sea. The proportion of carnivores remained similar at all stations. Non-Metric Multidimensional Scaling (nMDS) ordination for epifaunal trophic groups clearly demarcated higher salinity/pH stations from lower salinity/pH stations, suggesting different trophic compositions along the estuarine pH gradient. 相似文献
10.
采用扩散模型法与实验培养法对鄱阳湖沉积物和水界面间可溶性总磷和可溶性磷酸盐的界面交换过程进行研究,并探讨了其影响因素.结果表明,利用2种方法得到鄱阳湖各站点可溶性总磷和可溶性磷酸盐在沉积物与水界面间的交换方向不完全相同,大部分站点沉积物是磷的源,其中,利用扩散模型法估算的可溶性总磷和可溶性磷酸盐平均扩散通量分别为0.052和0.047 mg/(m~2·d),而实验培养法测得可溶性总磷和可溶性磷酸盐的平均交换通量则分别为0.25和0.24 mg/(m~2·d),且各站点利用扩散模型法测得磷的交换通量均小于实验培养法的计算结果.此外,上覆水溶解氧浓度及水体温度对可溶性总磷和可溶性磷酸盐的交换过程均具有一定的影响,表现为温度越高,溶解氧浓度越小,可溶性总磷和可溶性磷酸盐的交换越强烈. 相似文献
11.
Elisabete S. Braga Vitor C. Chiozzini Gláucia B.B. Berbel João C.C. Maluf Valquíria M.C. Aguiar Marcela Charo Daniel Molina Sílvia I. Romero Beatriz B. Eichler 《Continental Shelf Research》2008
Nutrient distributions observed at some depths along the continental shelf from 27°05′S (Brazil) to 39°31′S (Argentina) in winter, 2003 and summer, 2004 related to salinity and dissolved oxygen (mL L−1) and saturation (%) data showed remarkable influences of fresh water discharge over the coastal region and in front of the La Plata estuary. In the southern portion of the study area different processes were verified. Upwelling processes caused by ocean dynamics typical of shelf break areas, eddies related to surface dynamics and regeneration processes confirmed by the increase of nutrients and the decrease of dissolved and saturation oxygen data were verified. High silicate concentrations in the surface waters were identified related to low salinities (minimum of 21.22 in winter and 21.96 in summer), confirming the importance of freshwater inputs in this region, especially in winter. Silicate concentration range showed values between 0.00 and 83.52 μM during winter and from 0.00 to 41.16 μM during summer. Phosphate concentrations worked as a secondary trace of terrestrial input and their values varied from 0.00 to 3.30 μM in winter and from 0.03 to 2.26 μM in summer; however, in shallow waters, phosphate indicated more clearly the fresh water influence. The most important information given by nitrate concentrations was the presence of water from SACW upwelling that represents a new source of nutrients for marine primary production. Nitrate maximum values reached 41.96 μM in winter and 33.10 μM in summer. At a depth ∼800 m, high nitrate, phosphate and silicate concentrations were related to Malvinas Current Waters, Subantarctic Shallow Waters and Antarctic Atlantic Intermediate Waters (AAIW). Dissolved oxygen varied from 3.41 to 7.06 mL L−1 in winter and from 2.65 to 6.85 mL L−1 in summer. The percentage of dissolved oxygen saturation in the waters showed values between 48% and 113% in winter and from 46% to135% in summer. The most important primary production was verified in the summer, and situations of undersaturation were mainly observed below 50 m depth and at some points near the coast. The anti-correlation between nutrients and dissolved oxygen which showed evident undersaturation also revealed important potential sites of remineralization processes. The nutrient behaviours showed some aspects of the processes that occur over the Southwestern South Atlantic continental shelf and in their land–sea interfaces between Mar del Plata and Itajaí. 相似文献
12.
Initial coagulation rates of colloidal hematite (-Fe2O3) particles (diameter less than 0.1 µm) were measured experimentally in well-defined laboratory systems at constant temperature. The relative stability ratio,W, was obtained at various ionic strengths in NaCl medium and at pH values in the range from 3 to 12. ExperimentalW values ranged from 1 to 104 in various systems. The results delineate the roles ofspecific andgeneralized coagulation mechanisms for iron oxides. Among the specifically-interacting species (G
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) studied were phosphate, monomeric organic acids of various structures, and polymeric organic acids. The critical coagulation-restabilization concentrations of specifically-interacting anions (from 10–7 to 10–4 molar) can be compared with the general effects of non-specific electrolyte coagulants (10–3 to 10–1 molar). The laboratory results are interpreted with the help of a Surface Complex Formation/Diffuse Layer Model (SCF/DLM) which describes variations of interfacial charge and potential resulting from variations of coagulating species in solution. Comparison of these laboratory experiments with observations on iron behavior in estuarine and lake waters aids in understanding iron removal mechanisms and coagulation time scales in natural systems. 相似文献
13.
Conceptual models of circulation theorise that the dominant forces controlling estuarine circulation are freshwater discharge from the riverine section (landward), tidal forcing from the ocean boundary, and gravitational circulation resulting from along-estuary gradients in density. In micro-tidal estuaries, sub-tidal water level changes (classified as those with periods between 3 and 10 days) with amplitudes comparable to the spring tidal range can significantly influence the circulation and distribution of water properties. Field measurements obtained from the Swan River Estuary, a diurnal, micro-tidal estuary in south-western Australia, indicated that sub-tidal water level changes at the ocean boundary were predominantly from remotely forced continental shelf waves (CSWs). The sub-tidal water levels had maximum amplitudes of 0.8 m, were comparable to the maximum tidal range of 0.6 m, propagated into the estuary to its tidal limit, and modified water levels in the whole estuary over several days. These oscillations dominated the circulation and distribution of water properties in the estuary through changing the salt wedge location and increasing the bottom water salinity by 7 units over 3 days. The observed salt wedge excursion forced by CSW was up to 5 km, whereas the maximum tidal excursion was 1.2 km. The response of the residual currents and the salinity distribution lagged behind the water level changes by ∼24 h. It was proposed that the sub-tidal forcing at the ocean boundary, which changed the circulation, salinity, and dissolved oxygen in the upper estuary, was due to a combination of two processes: (1) a gravity current generated by a process similar to a lock exchange mechanism and (2) amplified along-estuary density gradients in the upper estuary, which enhanced the gravitational circulation in the estuary. The salt intrusions under the sub-tidal forcing caused the rapid movement of anoxic water upstream, with significant implications for water quality and estuarine health. 相似文献
14.
A double-spike method was used to obtain Mo isotope data for sediments and waters of the seasonally anoxic Chesapeake Bay, and its primary tributary, the Susquehanna River. The dissolved Mo distribution in the estuary is non-conservative, reflecting minor Mo loss to the sediments, although removal of Mo to the sediments does not have a large influence on the isotopic composition of the water column. The δ98Mo of dissolved Mo in most of the estuary is dominated by seawater. Six samples with salinity > 15 have an average δ98Mo = + 2.17‰ (± 0.12), which agrees well with a δ98Mo value for the CASS-4 seawater standard of + 2.23‰. A single sample of Susquehanna River water has a δ98Mo of + 1.02‰, consistent with recent findings of positive δ98Mo in rivers worldwide. Susquehanna river sediments, in contrast, have δ98Mo ～ ? 0.1‰. The difference between the river water and sediment values implies that isotopic fractionation occurs within the river basin. The δ98Mo values for estuarine sediments are offset from values in the overlying water. Most samples deposited before 1925 have δ98Mo less than 0‰, similar to the Susquehanna sediments. Subsequently, there is an increase in the variability of δ98Mo, with values ranging up to + 0.8‰. The transition to increased variability coincides with the onset of authigenic Mo deposition, which was previously attributed to escalating summertime anoxia. Authigenic Mo concentrations correlate poorly with δ98Mo in core samples, suggesting that independent mechanisms influence the two parameters. Authigenic Mo concentrations may be controlled by shifting pore water H2S levels, while δ98Mo may be primarily affected by annual variations in Mn refluxing. 相似文献
15.
Zeng Zhou Luying Chen Jianfeng Tao Zheng Gong Leicheng Guo Mick van der Wegen Ian Townend Changkuan Zhang 《地球表面变化过程与地形》2020,45(3):590-604
Salinity difference between terrestrial river discharge and oceanic tidal water plays a role in modifying the local flow field and, as a consequence, estuarine morphodynamics. Although widely recognized, recent numerical studies exploring the long-term morphological evolution of river-influenced estuaries with two-dimensional, depth-averaged models have mostly neglected salinity. Using a three-dimensional morphodynamic model, we aim to gain more insight into the effect of salinity on the morphodynamics of fluvio-deltaic systems. Model results indicate that the resultant estuarine morphology established after 600 years differs remarkably when a salinity gradient is included. A fan-shaped river-mouth delta exhibits less seaward expansion and is cut through by narrower channels when salinity is included. The inclusion of salinity tends to generate estuarine circulation, which favours landward sediment transport and hence limits the growth of the delta while enhancing the development of intertidal areas. The formation of deltaic channel–shoal patterns resulting from morphodynamic evolution tends to strengthen salinity stratification, which is characterized by an increased gradient Richardson number. The direction of the depth-averaged residual sediment transport over a tide may be opposite to the direction of residual velocity, indicating the significant influence of baroclinic effects on the net sediment transport direction (and hence morphological change). The effect of salinity on morphological evolution becomes less profound when the strength of tidal or fluvial forcing is dominant over the other. The effects of sediment type and flocculation, which are particularly important when salinity gradients are present, are also discussed. Overall, this study highlights that neglecting salinity to simulate long-term estuarine morphodynamics requires more careful justification, particularly when the environment is characterized by fine sediment types (favouring suspended transport), and relatively large river discharge and estuarine depth (favouring baroclinic effects). © 2020 John Wiley & Sons, Ltd. 相似文献
16.
Several studies have provided evidence for the enrichment of trace elements in coastal waters, particularly for copper. These enrichments have been attributed to diffusion from continental shelf sediments and to an influx of river water. We attempted to resolve between these sources by undertaking an extensive suite of measurements of trace metals (Cu, Ni, Cd), 226Ra and 228Ra in the surface waters of the Gulf of Mexico, along with trace metal profiles at 6 stations (April 1981 and December 1982). These data establish that enrichments of copper, nickel and cadmium occur in the shallow waters of the Gulf of Mexico. On the Mississippi continental shelf, high trace element concentrations (Cu, Ni: ～ 9 nmol/kg; Cd: ～ 200 pmol/kg) in lower-salinity waters (26‰) are similar to those observed in the Mississippi plume at the same salinity. This evidence suggests a river water source. On the other hand, trace element enrichments are also observed in the northern Gulf (Cu: +0.4 nmol/kg; Ni: +0.5 nmol/kg; Cd: +20 pmol/kg) which coincide with an increase in 228Ra but are not accompanied by decreased salinity. The excess of evaporation over precipitation in this region makes it possible that this water could be evaporated estuarine water; therefore, hydrographic observations cannot distinguish readily between river and shelf sources. A regional flux balance shows that most of the excess copper in the surface waters of the Florida Current can be supplied by the river-borne dissolved copper flux. Within the uncertainties of such calculations, the continental shelf copper flux must be less than or equal to the river flux. 相似文献
17.
Pradeep K. Aggarwal Luis Araguas‐Araguas Manzoor Choudhry Michel van Duren Klaus Froehlich 《Ground water》2014,52(1):20-24
Uptake of atmospheric CO2 during sample collection and analysis, and consequent lowering of estimated ages, has rarely been considered in radiocarbon dating of groundwater. Using field and laboratory experiments, we show that atmospheric CO2 can be easily and rapidly absorbed in hyperalkaline solutions used for the extraction of dissolved inorganic carbon, resulting in elevated 14C measurements. Kinetic isotope fractionation during atmospheric CO2 uptake may also result in decrease of δ13C, leading to insufficient corrections for addition of dead carbon by geochemical processes. Consequently, measured 14C values of groundwater should not be used for age estimation without corresponding δ13C values, and historical 14C data in the range of 1 to 10% modern Carbon should be re‐evaluated to ensure that samples with atmospheric contamination are recognized appropriately. We recommend that samples for 14C analysis should be collected and processed in the field and the laboratory without exposure to the atmosphere. These precautions are considered necessary even if 14C measurements are made with an accelerator mass spectrometer. 相似文献
18.
This study investigates the influence of Ca2+ and Mg2+ on the removal of F? by magnesium potassium phosphate (MPP) from water. The kinetic experiments reveal that the F? concentration decreased from 3.5 to 3.31 mg L?1 in a single (F?) system and to 1.45 mg L?1 in a ternary system (F?, Ca2+, and Mg2+) after 1 min, respectively. Thus, the F? removal efficiencies are found to increase by about 53% with the co‐active effect of Ca2+ and Mg2+ in the solution. Moreover, Ca2+ and Mg2+ are almost completely removed in the F?, Ca2+, and Mg2+ system. According to the pseudo‐first‐order modeling, the rate constants k for F?, Ca2+, and Mg2+ are 0.00348, 0.0106, and 0.0159 min?1 respectively; thus, Mg2+ > Ca2+ > F?. In the ternary system, the removal efficiencies are 53.29–66.03% for F?, 99.99–100% for Ca2+, and 87.21–95.19% for Mg2+ with initial pH 5–10. The removal efficiencies of F? increases with increases in initial concentrations of F?, Ca2+, and Mg2+. The removal of F? is governed by two routes: 1) adsorption by electrostatic interactions and outer sphere surface complexation; 2) co‐precipitation with Ca3(PO4)2, CaHPO4, Mg3(PO4)2, and Mg(OH)2. 相似文献
19.
New measurements of dissolved vanadium in a variety of rivers and estuaries are presented here. The data indicate that the average concentration of dissolved vanadium in major rivers entering the ocean is 15 nmol/kg. Weathering rate and type of source rock, rather than solution chemistry or anthropogenic influences, appear to be the important factors in determining fluvial dissolved vanadium concentrations. Laboratory experiments suggest that in oxic waters vanadium is found predominantly in its most oxidized, anionic form (V(V)). Complexation with organic matter and formation of large colloidal species appear to be unimportant. Adsorption also appears to be a less important influence for vanadium than for some other trace elements such as zinc.In estuaries, vanadium behaves as a bioactive element, showing a close correspondence with the distribution of phosphate. The extent of estuarine vanadium removal is presently uncertain but may be low due to rapid remineralization of this element. Based on the river flux, the oceanic residence time for dissolved vanadium is estimated to be 100,000 years. 相似文献
20.
The relations between lake surface sediment diatoms and water environmental variables were revealed effectively by use of a new multivariate canonical correspondence analysis (CCA) based on 45 lakes in the Tibetan Plateau. Water depth, conductivity, Cl?, Mg2+, K+ and pH, identified from 12 contemporary water environmental variables, can significantly and independently explain the diatom distributions (p<0.05). The first two axes (λ1=0.34, λ2=0.27) capture 16.1% of the variance in the species data, and account for 57.4% of the variance in diatom-environment relationship. The deletion of redundant environmental variables and unusual samples do not influence the explanation to diatom data. The final CCA result indicates that the water depth and the salinity are the two important environmental gradients and influence the diatom distribution in the plateau lakes. The water depth correlates with axis 1, while conductivity, Cl?, Mg2+ and K+, indicating the direction of salinity changes, correlate with both of the first two axes. The definition of diatom-environment model may provide a basis for further quantitative inference on diatom-environment transfer function. 相似文献